goodcoffeecode

TomB - ha! It went in perfectly. Clean, drilled hole and new switch lines up with existing controls in order to satisfy my OCD

Yeah, I know what you mean. I think there's real benefit, however, in getting the relay installation with the "on" light. I really need to be able to drive this on Tuesday, and I'm not sure the new switch will arrive in time. This is a sub-£10 fix

In the meantime, I'm pretty pleased with this. It's a bit Heath Robinson, but I've fitted an override switch. I saw a post detailing relays and lights, but that's way beyond my current electrical abilities! I just added a couple of piggyback spade things to the cooling fan switch, passed some 17A wire through an existing hole in the bulk head, drilled a new hole in the dashboard and put in a new switch. Works like a charm

I think we have a winner! Unscrewed the cooling fan switch (and lost about half a cup of coolant). So, firstly, this does seem to now be submerged in the fluid. Disconnected both wires from the switch and shorted them together. Turning on ignition starts the fan. Connected wires back to switch and then submerged it in boiling water for a few minutes. Fan did not come on. So, on the assumption that it doesn't take longer for it to get up to temperature, it looks like the switch has failed. Also, because all the hoses got nice and hot on the second start, I think I'm happy that the thermostat is OK. I'll test that hypothesis (once the new switch is fitted) by started the engine with a little gap in either the hex screw or bleed tee.

SECOND UPDATE: Yes, I did fill it whilst it was slightly pointing downhill :(. Once cool (after the first startup) I topped up the radiator via the hex screw. I also removed some more coolant from the expansion tank with the turkey baster. I then did a second start (both starts were done on the flat). This time the temp stayed at around 80c for at least 10 minutes. Once again the expansion tank filled with coolant - still not sure if this is normal? Given its name, maybe? Oddly, the temp then rose to 90/95, stayed there for a minute, then dropped back to 80. However, the fan never came on. The temperature then crept up to nearly 100 - again no fan. When I pulled out the heater lever and put the fan on, only cold air came out. I suspect there's an airlock at that end now, but I'll get rid with the bleed tee once cool. So, I'm think the fan sensor thing has failed. The fan itself seems to be good as I can force it on by connecting the 2 wires.

UPDATE... Firstly, I rolled the car down the slight slope from the garage to tip it forward. I then pulled the heater thing in the car to open that circuit. Removing both the top and bottom hex screws resulted in about 1 litre coming out. When I cut the top heater hose (to fit the bleed tee), about another litre came out. Once the bleed tee was fitted, blowing into it forced another volume of coolant out. Once suitably drained, I screwed the bottom hex screw back in. I poured 50:50 G40 into the bleed tee until I saw coolant coming from the top hex opening. I then screwed that back in. I continued until coolant was in the expansion tank. Squeezing the large hose connected to the top of the radiator allowed more coolant to go in the bleed tee. I think I should have put the expansion tank cap back on earlier. For a while, I could pour coolant into the bleed tee, which wasn't topped, and the expansion tank would further fill. Once on level ground, I used a turkey baster to remove excess coolant from the expansion tank! When I ran the engine, it took about 5-10 minutes to get up to just under 90c. The top fat hose was hot, as were the 2 smaller hoses going to the heater. When I opened the heater lever, the remainder of those small hoses also got hot. However, the lower fat hose connecting to the radiator remained cold. The fan never switched on. I could have run it longer but, as you can see from the photos, the expansion tank was getting very full. I'm going to wait until everything has cooled down and then open top hex screw to see if there's an airlock there. It feels as though this isn't quite fixed, so interested in people's thoughts please. Thanks.

Excellent, thanks John.

OK, so I now have all the parts I need (Expansion tank cap, Bleed Tee, hose clamps, coolant). My plan is to: Fully open the heater lever near my right knee (by pulling it towards me). Remove the lower hose from the radiator in order to drain all the coolant. Randomly squeeze and massage the hoses in order to remove any stubborn fluid. Cut the top heater hose with a box cutter, insert the Bleed Tee, and affix 2 hose clamps to secure it in place. Replace the lower hose to the radiator! Remove the expansion tank cap Add coolant via the Bleed Tee until I see coolant appearing in the expansion tank Unscrew the hex thingy at the top of the radiator in order to help get rid of any air Continue adding coolant to the Bleed Tee until it comes out the hex thingy. Tighten the hex thing Screw the cap on the Bleed Tee Screw on the new expansion tank capI'll then run the engine, let it get warm, check the levels in the expansion tank, and confirm that the fan comes on as expected. Once cool, I'll also take a look in the hex thingy to make sure there's no air. Questions: I'm guessing I'll dilute the coolant 50:50. Is that correct? Have I identified the correct place to insert the Bleed Tee in the attached photo (white hatched rectangle)? Should I first will with water and run the engine in order to "clean" the system? Have I missed anything?

nutty7 - I'll check the logs...

Thanks JV. Bleed Tee ordered. Already ordered a new pressure cap and the G30 (both should be here by tomorrow). Given that I could add more than a pint of water to the radiator, isn't it more likely that the fan switch works, but it just wasn't in the fluid? Or, are you suggesting changing it "just in case"? How does one ensure the heater valve is open (and where is it!)? Thanks.

Got it. What temp does the mechanical thermostat normally open at?

Here's the video of the incident:

Hi John, I didn't check those - but I will tomorrow. I'd only checked the other large pipe connecting to the rad. So, I must confess that I don't really know how this works. When you say "until the stat opens" do you mean that the coolant flow doesn't start (going through the rad?) until it reaches a certain temp? Presumably, there's then a second, higher, temperature where the fan kicks in (82?).

Pulled out both wires going into thermo switch (#2 in pics), and held them together with some locking pliers. Turned on ignition and fan came on straight away. I then started the car and it took about 4 minutes for the temperature gauge to read 60. Not sure if that suggests whether or not the gauge is working correctly though. The top red hose (which, I believe, comes from the engine?) got warm in places, but the radiator stayed cold. As soon as it was turned off I also took the liberty of checking the oil - which was spot on.

Hi Ian, Thanks for that. Are you sure about shorting those 2 wires together? (I assume that means "unplug them and touch them together"?). Someone else has suggested definitely not to do that. Thanks, Chris